A half-bridge circuit includes a high-side switch and a low-side switch that each include a load path and a control node and that have their load paths connected in series. Usually, an output of the half-bridge is formed by a circuit node to which the load paths of both the high-side switch and the low-side are connected. Further, a series circuit with the high-side switch and the low-side switch may receive a supply voltage that is available between supply nodes.
A half-bridge circuit can be employed in a variety of different circuit applications such as voltage inverters, buck converters, or drive circuits for driving loads, to name only a few. Operation of a half-bridge circuit may include a switched-mode operation of the high-side switch and the low-side switch. Such switched-mode operation may result in abrupt changes of a current through one of the high-side switch or the low-side switch. In particular, such abrupt changes may occur if one of the high-side switch or the low-side changes from an on-state, in which it is conducting a current, to an off-state, in which it blocks. Abrupt changes of a current through one of the high-side switch or the low-side may induce voltage spikes with a voltage level much higher than the supply voltage in parasitic inductances of conductors that connect the high-side switch and the low-side of the half-bridge and that connect the half-bridge to the supply nodes.
At a given parasitic inductance, the more abrupt the current changes, the higher the voltage level of the voltage spike. In order to keep the voltage spikes below a certain voltage level, a switching speed of the high-side switch and the low-side switch may be reduced. This, however, increases switching losses. Another option would be to design the high-side switch and the low-side switch with a voltage blocking capability high enough to withstand the voltage spikes. Increasing the voltage blocking capability, however, may increase the on-resistance, which is the electrical resistance of the respective switch in the on-state, and, therefore, the conduction losses. Increasing the voltage blocking capability may also increase the switching losses, which are losses associated with switching on and switching off the transistor device.